Vibrating screen



.lune 26, 1923. L45946 B. A. MITCHELL VIBRATING S CREEN 1920 4Sheets-Sheet l W] TNESS: I N VEN TOR.

E. A. MATCHELL.

VIBRATING SCREEN ATTORNEYS VIBRATING SCREEN Filed Sept. 30, 1920Smmmiaet 3 WITNESS: INVESTOR.

June 26, 1923. 1,459,846

B. A. MITCHELL VIBRATING SCREEN Filed sept. 5o. 1920 4 shun-sheet 4 y 0.9% /0 975 @MMm /1 y@ *j/ W Y W57 i lll Yg; Y gg! `|""mluggggg 8,9@ l 55WI TNESS: I N VElVTOR.'

ATTORNEY titl 'Patented June 26, 1923.

BENJAMIN A. MITCHELL, OF GARFIELD, UTAH.

VIBRATING SCREEN.

Application led September 30, 1920. Serial No. 418,844.

To-aZZ lwhom it may concern Be it known that I, BENJAMIN A. MITCHELL, acitizen of the United States, residing at Garfield, in the county ofSalt Lake and State of Utah, have invented certain new and usefulImprovements in Vibrating Screens, of which the following is a sification.

his invention relates to improvements in vibrating screens and itspurpose is to provide screening apparatus having improved means formounting the screen cloth and imparting vibrations thereto.

he principal object of the invention is to provide a screening machinein which the screening medium is supported entirely by the-.vibraton Afurther object is to provide a screening machine having a plurality ofscreening units whichare vibrated simultaneously but out of phase witheach other. Still another feature is the provision of a screeningmachine comprising improved means for supporting the screening mediumand for creating minute vibrations therein which describe closed pathsin planes perpendicular to the screening medium. Other objects relate tovarious features of construction and arrangement which will appear moreclearly hereinafter. l f

The nature of the invention will be understood from the followingspecification taken in connection with the accompanying drawings inwhich two embodiments are illustrated.

lln the drawingsj Figure 1 shows an end elevation of one forlin of theimproved screening machine, the? walls of the feeding hopper and of thechamber for receiving the materials to be screened being shown insection;

Fig. 2 shows a perspective view of the under side of the screeningmachine, a portion of the supporting frame being broken away;

Fig. 3 shows a perspective view of the screening machine lookingdownwardly toward the upper side thereof;

Fig. 4 shows a longitudinal sectional View through the vibratoremployed, the section being taken on the line 4-4 of Fig. 1;

Fig. 5 shows a vertical section on the line 5 5 of Fig. a;

Fig. 6 shows a` longitudinal sectional View throu h a modified form ofthe screening machine in which the screening medium is mounted as asingle unit, the rotary vibrator and a portion of the supporting framebeing shown in elevation; and

Fig. 7 shows a transverse sectional View on the line 7--7 of F ig. 6.

The screenin machine as illustrated in Figs. 1 to 5, inc usive,comprises a supporting frame having a transverse frame member 10 formedintegrally with two side frame members 1l which are parallel to eachother. The side frame members are provided at their upper ends withprojecting pins 12 adapted to engage sockets 13 in supporting brackets14 which are secured to the vertical wall 15. The lower ends of the sideframe members 11 are provided with enlarged bosses 16 having threadedapertures extending vertically therethrough; These apertures are engagedby adjusting screws 17 lwhich are arranged with their lower ends seatingupon a supporting plate 18 carried by the upper edge of the wall 19. Thewall 19 is spaced from the wall l5 to form an intermediate chamber 20adapted to receive the screened materials which pass through thescreening apparatus carried by the supporting frame 10. The adjustingscrews 17 may be secured in position by lock nuts 21, thereby maintaininthe supporting frame at any desired ang e.

The loose materials such as crushed ore, coal, gravel, or the like,which are to be screened are distributed onto the screening medium froma discharge chamber 23 which is mounted along the upper edge of the wall15. The materials are discharged in a thin stream throughout the lengthof the screening machine, as shown at 24, by means of a rotary screwconveyer 25. The crushed materials are discharged onto the screwconveyer 25 and into the disharge chamber 23 from a hopper 26.

The screening machine is vibrated by means of the vibrator designatedgenerally by the numeral 30. This vibrator has a casing 31 whichAconsists of an enlarged central portion 31a and two projecting endportions. 31b of reduced diameter. The vibrator casing extends parallelto the frame member 1() and is supported thereby, bein secured theretothrough a strap 32 whic extends around the central part of the enlargedportion 31 of the Casin This strap is provided at its ends with threadedbolts 33 which engage ears 34 formed integrally with the frame member 10on opposite sides thereof. The ends of the bolts 33 are engaged by nuts35 which may be adjusted in order to regulate the pressure with whichthe vibrator casing is held in position on the frame member. The centralpart of the vibrator casing is provided with a projection 36 whichcarries a cap 37 having a substantially spherical surface formed thereonand adapted to seat in a corresponding recess formed in the upper partof the frame member 10 so that a limited' vibratorymovemerit of thecasing 31 is permitted, depending upon the degree of tension in theholdingstrap 32.

he vibrator casing is formed in two sections, as shown partlcularly inFig. 4, and the two parts are secured together by means of elongatedbolts 38, which extend through the enlargedportions 31a of the casingand through apertures which are formed in the end walls 31c by which the`central part of the casing is connectedto the projecting end portions31h. A longitudinal-shaft 40 eX tends throughout the vibratorfeasing andis journaled in bearings formed in the bearing members 41. Thesevbearingmembers have enlarged parts41a, which occupy the end portions of theenlarged casing 31a, and other reduced portions 41b which project intoand closely tit the reduced parts 31'b of the casing. The bearings forthe shaft 40 are formed in the reduced parts 41b and these portions areprovided with oil receiving recesses 42 from which oil is supplied tothe shaft 40 by oil rings 43. The vibrator shown is driven by anelectric motor the field frame and pole pieces 45 of which are mountedin position between the central parts 41a of the bearing members and thearmature 46 of the motor is secured on the central are pro ded throughthe bearing members and throu h the casing to permit the necessaryhventiation of the motor.

is vibrator utilizes the principle of rotating moments to producevibrations as set forth in my copending application, Serial No. 275,321.To this end bodies whose average mass center is eccentric te the axis ofrotation are employed. Accordingly there is provided roller cages 50which are secured respectively at each end of the shaft 40 each beinmounted between one of the bearing mem rs 41h and the end wall 51 of thecasing 31. Each cage 50 is provided on dia j metrically opposite sideswith a series of recesses 52 which are circular in cross section andarranged in a row parallel to the axis of the shaft 40. @ne row ofrecesses 52 in each cage 50 is adapted to contain a series of sp ericalballs 53 which travel around with the rotation of the cage and engageannular raceways 54 of hardened metal which are secured within thecasing and hollen/ed out on v with each other:

art of the shaft 40. Apertures 47 l their inner sides, as shown at 55,to form a separate annular track for each spherical ball. -The balls 53in one cage are preferably arranged on the opposite side of the shaft40from the balls in the other cage. As the shaft is rotated at acomparatively high speed, preferably about 360() revolutions per minute,the balls 53 are carried around in their raceWays by the cages 50 andthe effect of these rapidly rotating balls located eccentrically withrespect to the aXis of the shaft 40 is to cause each particle of thecasing 31 to travel in a minute closed path. As will b e observed, thevibrations in the opposite ends of the casing 31 are displaced in phasefrom each other by substantially 180 degrees. The end portions of thecasing are preferably filled with oil in order to reduce the frictioncreated by the rotation of the spherical balls. i

The vibrationsthus setup in the vibrator casing` are transmitted to thescreening medium through transmitting members 6U. In the form lof theinvention illustrated in Figs. 1, 2, and 3, these transmitting memberscomprise arms 61 which diverge upwardly from collars 62. These collarsare adapted to tit the tapered end portions 63 of the vibrator casing 31and they are secured in position'thereon by transverse keys 64 whichengage keyways in the projecting end flanges 65 of the vibrator casing.Each arm 61 carries at its-upper end a transversely extending channelmember 66,'the `channel members carried by opposite transmittingmeinbers 6() being arranged in alinement A screen frame 67 is carried byeach transmitting member'60, each frame comprising Wooden side framemembers 68, end frame members 69, and a centra] transverse frame member70. The end frame members 69 are seated in the channel members 66 andare secured thereto by bolts 71. The side frange members 68 are securedbolts 75. lTwo rigid frame members 67 of wooden construction are thusformed and each frame is supported independently of the other on one ofthe transmitting members 60 so that each particle of each screen frameis vibrated in a closed path out of phase with the vibrations of theother frame. The woven wire screen cloth 77 is secured to each frame 68by means of a series of double pointed tacks 78 which engage the woodenframe members, thus. holding the si'reen cloth in a taut condition onthe supporting frame. As the vibrator is o erated and the crushedmaterials are passe downwardly. thereover, they are thoroucrhly screenedby the action of the screen clooth, each particle of which describeswith subist Maaate stantially uniform amplitude the path of the orbit ofthe transmitted vibration in a plane which is perpendicular to the planeof the screen frame and also perpendicular to the axis of the rotaryvibrator, but parallel to the path of travel of the crushed mate- 'rialsover the screening medium. The inclination of the screening medium canbe regulated by changing the angle oi' the suppoing frame through themanipulation of the adjusting screws 17 and by regulating the angle ofthe screen cloth and the speed with which the crushed materials are fedto the screen surface, it is possible to eifect a very efficientscreening of the crushed materials before they reach the lower edge ofthe screen. A modified form of the invention is illus* trated in Figs. 6and 7 where the vibrator 80 is secured by a strap 81 to a transverseframe member 82 which may be similar to and mounted in the same way asthe supporting frame heretofore described. The projecting ends a of thevibrator, in which the minute circular vibrations are set up, carrytransmitting members 83 comprising plates 84 which have apertures 85therein adapted to be closely fitted by the end portions 86 of thevibrator casing. These plates are secured in position by keys 87 and theupper'edges thereof are secured by rivets 88 to the side -plates 89.These side plates extend upwardly and outwardly from the plates 84, asshown at 89a and terminate in parts 89" of angle form which arereinforced along their upper edges by angle irons 90. A screen frame 9 1is adapted to seat in the angle members 89h, as shown yin Fig. 6, thisscreen frame comprising wooden side frame members 92 connected bytransverse end members 93 of Wooden construction. These members arerigidly secured at their intersections and are connected to thesupportin members 89b by means of bolts 94. The screen frame 91 alsocomprises a number of iptermediate frame members 95 which extend betweenthe end frame members 93. The lateral spreading of the transmittingmembers 84 is prevented by a transverse tie rod 96 which is secured tothe frame by bolts 97 and connected to the side plates 89 by bolts 98.Ihe wooden frame 91 is thus mounted securely on the metallic frame andis carried entirely by the rotary vibrator. The screen cloth 100 ismounted on the wooden frame 91, being secured to the frame members bymeans of double pointed tacks. W hen the vibrator isoperating, two setsof vibrations displaced vin phase from each other are set up in thescreen cloth. This form of the invention and the one previouslydescribed are particularly adapted for screen cloth of relatively linemesh since the cloth is ri idly supported in a taut condition and is eectively vibrated without 'the necessity poses of illustration, itwillbe understood that it may be constructed in various other forms withoutdeparting from the scope of the appended claims.

I claim 1-. In a screening machine, the combination with a vibratorhaving a casing adapted to execute. vibration in paths forming closedorbits, of a plurality of supporting devices respectively mounted ondilierent parts of said casing, and screens on each of said devices. f f

ti'on with a vibrator having a casing centrally mounted and providedwith projecting ends adapted t0 execute harmonic motion in planestransverse to the axis of symmetry, ot' supporting devices respectivelymounted on the ends of said vibrator and arranged to be in differentphases when said vibrator is in motion, and screens carried by each ofsaid devices.

8. In a screening machine, the combination with a vibrator having acasing centrally mounted and provided with projecting tubular endsadapted to be internally actuated to execute harmonic motion in planesperpendicular to the axis of symmetry, of supporting devices mountedrespectively on each end of said vibrator and arranged vto be indifferent phases when said vibrator is in motion, a screen frame carriedby each of said devices, and a screen secured in each screen frame.

4. In combination, a Vibrator, a pair of transmitting members securedthereto, a pair of screen frames each' mounted. independently on one ofsaid transmitting members, and a screen cloth mounted on each of saidframes.

5. In combination, a vibratonfa pair of transmitting members securedthereto, a pair of screen frames each mounted independently 'on one ofsaid transmittingmembers, a screen cloth mounted on each oit saidframes, and means for operating said vibrator to vibrate said framessimultaneously and out of phase with each other.

6. In combination, a vibrator casing, means for producing rotaryvibrations in the ends of said casing, transmitting members extendingfrom said Casin a pair of screen frames each mounted in ependently onone of said transmitting members, and a screen cloth mounted on each ofsaid fra-mes.

7. In combination, vibrator, means for producing vibrations havingdiderent phase relations in dierent parts of said casing, transmittingmembers extending from the diderent partsot said casing, a screen framemounted on each ot said transmitting mem- 2. In a screening machine, thecombinarot liti@ bers, and a screen cloth mounted on each of saidtrames.4

8. In combination, a vibrator, means for producing vibrations havingdifferent phase relations in different parts of said casing,transmitting members extending from the different parts of said casing,a screen frame mounted on each of said transmitting members, a screencloth mounted on each of said frames, means for supporting saidvibrator, and means for changing the inclination of said support to varythe inclination ofrsaid screens.

9. In combination, a supporting frame, means for pivotally supportingone edge of said frame, means for adjustably supporting the oppositeedgeof said frame, a vibrator mounted on an intermediate part of saidframe, and a screen carried by said vibrator.

10. In combination, a supporting frame, means for pivotally supportingone edge of said frame, means for adjustably supporting the oppositeedge of said frame, a vibrator mounted on said frame with its'axisparallel to the axis of movement of *said frame, transmitting memberssecured to said vibrator and extending transversely thereto, a screenframe carried by each of said transmitting members, and a screen clothmounted on each of said frames.

.axis parallel to the axis of movement of said frame, transmittinmembers secured to said vibrator and exten ing transversely thereto,

a wooden screen frame mounted 1n an in' clined position on each of saidtransmittin members, and a screen cloth tacked on eac of said Woodenframes.

l2. In combination, a supporting frame, means for pivotally supportingone edge of said frame, means for adjustably supporting the oppositeedge of said frame, avibrator mounted on said frame with its axisparallel to the axis of movement ofl said frame, transmitting memberssecured to said vibrator and extending transversely thereto, a Woodenscreen vframe mounted in an inclined positionl oneach of saidtransmitting members, a screen cloth tacked on each of said woodenframes, and means for causing loose materials to pass downwardly oversaid kscreen cloth to planes perpendicular to the axis of said Vibrator,

In testimony whereof, I have subscribed my name BENJAMIN A. MITCHELL.

